On October 28, Pope Benedict XVI addressed the Pontifical Science Academy and urged them to avoid two extremes. Some treat science as the solution to every problem and the only authentic way to knowledge, while others fear science and distance themselves from it. The Holy Father said, “Science, of course, is not defined by either of these extremes. Its task was and remains a patient yet passionate search for the truth about the cosmos, about nature, and about the constitution of the human being.” Science should not be feared, for its truths will never contradict the truths of our faith.

On September 29, NASA and NSF-funded research found a planet in another solar system that orbits its host star right in the middle of the circumstellar habitable zone. This potentially habitable planet, called Gliese 581g, was discovered from the W. M. Keck Observatory in Hawaii.

For centuries people have hypothesized the existence of life on other planets. Since the outbreak of the Copernican Revolution, when modern science’s pioneers conjectured that the planets were not made out of ether but out of ordinary elements, some scientists even expected to find life on Mars, Venus, and the other planets, as well as on the Moon. Only in the past century have we been able to observe and explore our solar system, and in recent years scientists have finally begun to discover how difficult it is for the physical and chemical conditions necessary for life to come together at the right place and at the right time. Objective evidence tells us that by no means is Earth a typical chunk of rock in a normal sector of space. Those who adhere to the so-called Copernican Principle and assert that our planet is typical have quite a bit of explaining to do.

The empirical facts support the contrary thesis: our beloved planet is providentially located in a special spot in the universe, a safe distance from our galactic nucleus and outside the galaxy’s spiral arms. Within each galaxy most stars are located where cosmic dangers rule out the possibility of life, and not all stars that do in fact lie in the galactic habitable zone have planets of the right amount of mass orbiting where water could exist in liquid form. Up to this point there are only two known planets: Earth and Gliese 581g.

Future scientific observations will have to tell us whether Gliese 581g actually does have liquid water as well as other elements on which life is based. Even then, the chances that life could spontaneously arise from inert matter are less than the chances that a shower of asteroids could smash into the Earth and leave craters that spell out the words “E.T. phone home.” Chance simply does not provide a sufficient explanation for the existence of life. Stubborn atheists, however, can always say that although it would be extremely improbable for life to arise—and intelligent life, too— after all, it’s not absolutely impossible. Hey, we exist. What a lucky fluke of nature, right? Teleological reasoning provides a much more probable rational explanation for life’s origin here on Earth, and only the same reasoning can apply to other solar systems, as well. Life arising by chance is so improbable that if it is in fact found elsewhere, it would only be a stronger support for the existence of a Designer. Desperate scientists have even proposed silicon-based life as possible in regions where carbon is scarce. The only evidence we have contradicts this proposal.

Disheartened at the prospects of finding life nearby, scientists have by now turned their instruments toward other solar systems. Since the’90s over a hundred exoplanets have been discovered. In an interview in May of 2008, José Funes, SJ, Director of the Vatican Observatory, acknowledged that given billions of galaxies with billions of stars in each one, and supposing most of these could have planets, how could we exclude the possibility that life has developed elsewhere as well? If Gliese 581g has liquid water, it would undoubtedly be the best hope yet for extraterrestrial life. The presence of Gliese 581g in the center of the circumstellar habitable zone is, however, only one factor. There are several more difficulties life would have to surmount.

It is reported, in the last paragraph of the article released on NASA’s website, that the planet is tidally locked to its host star. This is the same phenomenon by which we always observe the same side of the Moon. One side of this planet is in perpetual daytime, always facing its host star, whereas the other side endures unending night. The penumbral line between the light and the darkness, which astronomers call the terminator, would be the most habitable spot on the planet. Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz, says that the planet’s surface climates would be more stable there. But what if its axis is unstable? Our Earth has a very stable axis, now tilting 23.5 degrees and varying only from 22.1 to 24.5 degrees over millennia, thanks to our Moon of irregularly large size (3,746 km in diameter) relative to Earth (12,756 km in diameter). In our solar system only Pluto’s satellite Charon is larger in proportion to its (dwarf) planet. This anomaly had led some recent scientists and philosophers to refer to us humans as inhabitants of the Earth-Moon system instead of mere inhabitants of Earth. More facts, strange but fortunate for life on Earth, could be cited, but let us bring a close to our consideration from the scientific perspective and touch on what other disciplines can contribute to this interesting inquiry.

Gliese 581g could have life, but how can we know for sure? Will an advanced civilization send back radio waves if we transmit them some? To travel 20 light years to get there using the fastest space ships we now have would take centuries.

“Are we alone?” is not a question science will soon be able to answer. If astronauts were to comb the Gliesian deserts and fish in Gliesian seas, and ultimately declare that life never originated on Gliese 581g, such a disappointment would not destroy all hope to find life elsewhere. Only an actual encounter with an extraterrestrial or the exploration of the entire universe could close the question about the possibility of extraterrestrial life once and for all.

And what about our Catholic faith? Does the Bible or any other source of revelation shed some light on this? Jesus offered his body for us once and for all (cf. Heb 1:10). But what if there are sinners on a distant planet? Might they too have to be redeemed?

Fr. Funes also confronts this question in the above mentioned interview. “The Incarnation,” he states, “is a unique and unrepeatable event.” If we find intelligent life, we might discover that, to use Christ’s image of the hundred sheep, we were the one sheep that went astray, falling into sin. Even if the extraterrestrials were sinners, it would still not be a problem for our faith. There would surely be some way in which they too could “rejoice in God’s mercy.” Who are we to put limits on God’s creative liberty?

As George Coyne, SJ, former Director of the Vatican Observatory, recently declared, the search for extraterrestrial life is interesting, but “what should surprise us is not that life could be discovered elsewhere in the Universe, but rather that in the Universe life exists.”

Pope Benedict XVI proposed two thoughts for further reflection, “First, as increasing accomplishments of the sciences deepen our wonder of the complexity of nature, the need for an interdisciplinary approach tied with philosophical reflection leading to a synthesis is more and more perceived. Secondly, scientific achievement in this new century should always be informed by the imperatives of fraternity and peace, helping to solve the great problems of humanity, and directing everyone’s efforts towards the true good of man and the integral development of the peoples of the world.”

Joseph A'Hearn, LC studies for the priesthood at the Pontifical University Regina Apostolorum in Rome.

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